[spazzpp2]

You'll probably get a lot of T-Rexes with trunks. I think, the reason for misinterpretation of skeletons is the missing information about other material than bones.

However, taking the hippo as an example, some convex bone shapes seem to be a hint for neighboring body fat and muscle. I'd check first, if current artists would do better after training themselves on living animals. Also, I'd check whether reptiles can get as fat as mammals, etc.

[k__]

True, but taking the hippo example, how likely is it that an animal has exposed teeth?

[jandrese]

There are plenty of animals with exposed teeth. Warthogs, alligators, narwhals, bumpheads, and more. I do agree with your premise that they are over-represented in dino art however.